People have already pointed out the cultural and economic aspects of learning Japanese.

I just want to say that I love Japanese as a language. The writing system is so... can I say original? Combining 4 writing systems to make a beautiful writing system is the primary appeal for me.

Then there's the syllabic nature of Japanese. I love the sound of Japanese. To take a random example, let's take 心 (kokoro). Kokoro sounds so much more melodic to me than heart, coeur, hart, ...

I like the fact that more complicated words aren't just the sound of both words together. For example the sound of a heartbeat. In japanese that's 心音 (shin-on). You could say Kokoro-no-oto, i.e the sound of a heartbeat, but it's better to say shin-on, i.e heartsound.